Term
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Definition
- x-rays pass through skin unimpeded
- hit film
- make it dark |
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Term
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Definition
- x-rays completely absorb by atoms in tissue
- do not hit film
- light area results
- occurs through photoelectric effect |
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Term
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Definition
- x-rays hit atoms and bounce in different direction
- results in film fog
- occurs through compton reaction |
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Term
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Definition
- increased dose to patient and possibly operator
- caused by scattered x-rays |
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Term
| Transmission is more likely |
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Definition
- high energy x-rays
- low absorbing material
- low density of atoms in material
- low thickness of absorbing material |
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Term
| Absorption is more likely |
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Definition
- low energy x-rays
- high absorbing material
- high density of atoms in material
- great thickness of absorbing material |
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Term
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Definition
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Term
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Definition
- high energy x-rays
- greater electron density |
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Term
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Definition
| - leads to scattered radiation |
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Term
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Definition
- degree of darkness of radiograph
- dark images have high ____
- light images have low ____ |
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Term
| radiographic density increased with |
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Definition
- increased exposure time, increase mA, increased kVp, and/or short cone
- image looks darker
- sensor exposed to greater numbers of x-rays |
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Term
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Definition
| greater x-ray exposure leads to ____ |
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Term
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Definition
| - difference in density btwn different parts of image |
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Term
| 3 components of radiographic contrast |
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Definition
- subject contrast
- film contrast
- viewing conditions |
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Term
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Definition
| - results from differential absorption of x-rays through different tissues of patient's body |
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Term
- soft tissue
- hard tissue |
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Definition
x-rays are transmitted through ____.
x-rays are absorbed by ____. |
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Term
| - different degrees of darkness |
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Definition
| difference in number of x-rays hitting film/sensor results in _____. |
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Term
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Definition
___ kVp produces images with low subject contrast.
___ kVp produces images with high subject contrast. |
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Term
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Definition
high kVp rays have greater penetration due to higher energy, so there is a gradual decrease in transmission with increasing thickness of steps.
- this causes gradual decrease in darkness
- therefore less difference in darkness btwn steps and ________ subject contrast. |
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Term
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Definition
- low kVp rays have less penetration due to lower energy
- decrease in transmission through steps is more drastic so there is greater darkness btwn steps
- therefore _____ subject contrast |
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Term
| long gray scale or long scale contrast |
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Definition
| - high kVp rays produce many shades of gray btwn black and clear (low contrast) |
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Term
| short gray scale or short-scale contrast |
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Definition
| - low kVp rays produce few shades of gray (high contrast) |
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Term
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Definition
- results from composition of film and processing conditions
- related to film speed, degree of exposure and film fog |
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Term
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Definition
| - sensitivity of film to exposure |
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Term
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Definition
| - requires less radiation to produce certain degree of density |
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Term
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Definition
- speed group ____ is slowest.
- speed group ____ is fastest. |
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Term
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Definition
| - When exposed/processed according to manufacturer's instruction there is ____ difference in contrast btwn different speed films. |
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Term
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Definition
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Term
| significant underexposure |
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Definition
- image too light
- little density difference btwn different tissues |
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Term
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Definition
- image too dark
- little density difference btwn different tissues |
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Term
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Definition
- range of exposure in which contrast and density are acceptable
- allows room for error without causing significant loss of contrast |
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Term
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Definition
- degree of unwanted darkness on radiograph
- caused by scattered radiation, light leaks, overheated developer, expired/warm film |
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Term
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Definition
- decreases contrast bcuz extra exposure increases darkness of all tissues, reducing difference in darkness
- reduced by long, rectangular PIDs by minimizing tissue exposure |
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Term
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Definition
- affects viewer's ability to detect contrast on film
- ideal: dark, quiet room |
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